The present invention generally relates to a magnetic recording apparatus, and particularly relates to super-fine processing technology that is used for manufacturing a magnetic head, and the like.
At present, hard disk drive units are widely used as mass external storage for a computer, and the like.
Presently, an inductive type thin film magnetic head (inductive head) that senses a magnetic field by induced current generated in a coil is used as the magnetic head of hard disk drive units. As the demand rises for faster operations in connection with increase of recording density, the latest hard disk drive units mainly use a magnetic sensor that employs a magnetoresistance element that directly detects a magnetic field.
Especially in the hard disk drive units of the latest technology, which are capable of high-density recording, a giant magnetoresistance (GMR) effect is adopted for the magnetic sensor. In a typical hard disk drive unit, an element that employs the giant magnetoresistance effect is formed on an Al2O3—TiC substrate, being compounded into one body with an inductive type writing head, and constituting a magnetic-head slider.
FIG. 1 is a perspective diagram showing a rough composition of the compounded type magnetic head formed by a thin film.
With reference to FIG. 1, a lower magnetic shield layer 31 made of a NiFe alloy etc. is formed by an electrolytic plating method through an Al2O3 film (not shown) on an Al2O3—TiC substrate (not shown) that constitutes the magnetic-head slider. On the lower magnetic shield layer 31, a magnetoresistance effect element 32 that has a spin valve structure is formed by a sputtering method through a gap spacer layer 31A (refer to FIG. 2) that is made of, e.g., Al2O3.
Patterning of the magnetoresistance effect element 32 is carried out into a predetermined form, and reading electrodes 33A and 33B that consist of an electric conductive film typically made of a Ta/Au/Ta laminate are further formed on both ends of the magnetoresistance effect element 32 on the gap spacer layer 31A.
The magnetoresistance effect element 32 is covered by another gap spacer layer (not shown) that is made of, e.g., Al2O3. Further, an upper magnetic pole layer 34 that is made of, e.g., a NiFe alloy is formed by an electrolytic plating method, and the like, on the gap spacer layer, the upper magnetic pole layer 34 constituting an upper magnetic shield layer. The upper magnetic pole layer 34 and the lower magnetic shield layer 31 may be separately formed.
Further, on the upper magnetic pole layer 34, a writing gap layer (not shown) made of, e.g., Al2O3 is prepared, and a writing coil 35 made of a Cu layer is formed by an electrolytic plating method through a first layer insulation film (not shown) including a resist, etc. Further, writing electrodes 36A and 36B are formed on both ends of the coil.
The writing coil 35 is covered by another layer insulation film (not shown) that is made of a resist, and the like. An upper magnetic pole layer 37, the tip of which constitutes a writing magnetic pole 38, is formed on the layer insulation film. The upper magnetic pole layer 37 and the writing magnetic pole 38 can be formed by electrolytic plating of the NiFe alloy layer using, for example, a resist mask (not shown).
When forming the upper magnetic pole layer 37 and the writing magnetic pole 38 by electrolytic plating, a resist mask is removed, ion milling using Ar ion is carried out such that the exposed section of the plating base layers is removed, an Al2O3 film is prepared on the whole surface such that a protective coat (not shown) is formed, and the substrate is diced such that individual chips are obtained. Further, slider processing that includes grinding and polishing processes is performed on each of the chips, and the length, i.e., the gap depth, of the writing magnetic pole 38 is adjusted. In this manner, the magnetic head slider that includes a reading head for reproduction using the magnetoresistance element 32, and a writing head for recording using the inductive type thin film magnetic head is obtained.
It is noted that the magnetoresistance effect element that constitutes the magnetic recording head used by the latest hard disk drive units is required to be further miniaturized corresponding to miniaturization of recording bits, accompanying increase of recording density.
FIG. 2 shows the composition of the magnetic sensor 32 used by the magnetic head of FIG. 1.
With reference to FIG. 2, the magnetic sensor 32 includes a magnetoresistance element 15 that has, e.g., spin valve structure and is formed on the Al2O3 film 31A that covers the lower magnetic shield layer 31. Further, hard bias patterns 16A and 16B made of a hard magnetic material are formed on both sides of the magnetoresistance element 15 on the Al2O3 film 31A.
Further, electrode patterns 33A and 33B, each being a laminate of a Ta film 33a, an Au film 33b, and a Ta film 33b, are formed on the hard bias patterns 16A and 16B. The tip section of each of the electrode patterns 33A and 33B extends on the upper surface of the magnetoresistance element 15, with a gap G formed in between. The gap G corresponds to the width of an effective optical core of the magnetic sensor using the magnetoresistance element 15.
FIG. 3 shows the structure of the magnetoresistance element 15 of FIG. 2 in more detail.
With reference to FIG. 3, the magnetoresistance element 15 includes a free layer 151 made of a ferromagnetic material layer, such as FeNi and a Co alloy, with its magnetization direction being changed by an external magnetic field, a non-magnetism electric conduction layer 152 including a Cu layer, etc. prepared on the free layer 151, and a pinned layer 153 having a fixed magnetization direction, and including a ferromagnetic material layer, formed on the non-magnetism electric conduction layer 152. The magnetization direction of the pinned layer 153 is pinned by a pinning layer 154 including a hard magnetic material layer such as CoCrPt, an antiferromagnetism layer, etc. formed on the pinned layer 153.
Further, the laminating structure including the free layer 151, the non-magnetism electric conduction layer 152, the pinned layer 153, and the pinning layer 154 is supported on both sides by the hard bias patterns 16A and 16B that consist of CoCrPt, etc., and the hard bias patterns 16A and 16B determine the magnetization direction of the free layer 151 in the state where there are no external magnetic fields.
Thus, the magnetoresistance element 15 has the so-called spin valve structure, and detects an external magnetic field in the form of magnetic resistance by passing a sense current I between the reading electrodes 33A and 33B. At this instance, by forming the reading electrodes 33A and 33B on the hard bias patterns 16A and 16B, respectively, with the tip sections extending on the surface of the magnetoresistance effect element 15, such that the so-called overlaid structure is formed, the sense current I can be provided, avoiding an insensitive zone formed near the border plane between the magnetoresistance effect element 15 and either of the hard bias patterns 16A and 16B. In this manner, the S/N ratio relative to magnetization signal detection is improved.
It is noted that, in the magnetic overlaid type sensor such as mentioned above, the optical core width part G between the tip section of the reading electrode 33A and the tip section of the reading electrode 33B participates in the performance of the magnetoresistance detection. Specifically, the smaller the optical core width part G is, the higher the spatial resolution of the magnetic detection is. That is, in order to detect magnetized spots that are densely arranged on a disk, it is desirable that the optical core width G be reduced as much as possible in reference to the structure of FIG. 3.
FIGS. 4A through 4H show a manufacturing process of a spin valve sensor that has the conventional overlaid structure.
With reference to FIG. 4A, a spin valve layer 15L is formed on the Al2O3 film 31A. At FIG. 4B of the process, the spin valve layer 15L is patterned by a resist pattern R1, which results in the spin valve structure 15 being formed.
Further, in FIG. 4B of the process, a CoCrPt film 16 is accumulated, and as a result, the hard bias patterns 16A and 16B are formed on the Al2O3 film 31A on both sides of the spin valve structure 15. FIG. 4B clearly shows that the CoCrPt film 16 is accumulated on the resist pattern R1.
Next, at FIG. 4C of the process, the CoCrPt film 16 is lifted-off with the resist pattern R1, and an organic polymer film 17 and a resist film R2, such as PMGI (poly dimethyl glutamid), are formed on the spin valve structure 15, so that the hard bias patterns 16A and 16B on both sides may also continuously be covered.
Then, at FIG. 4D of the process, the resist film R2 is exposed and developed, and a resist pattern R2A is formed. At FIG. 4E of the process, wet etching removes the organic polymer film 17 using the resist pattern R2A as a mask. At this time, due to a difference in the etching selectivity between the resist pattern R2A and the organic polymer film 17, the organic polymer film 17 receives lateral etching, and an organic polymer film pattern 17A smaller than an exposure limit is formed at the bottom of the resist pattern R2A as shown in FIG. 4F. Moreover, during the wet etching, the resist pattern R2A also receives lateral etching (slimming), and its size is reduced below the exposure limit. Thus, as a result of the organic polymer film pattern 17A receiving the lateral etching, an undercut 17B is formed directly under the resist pattern R2A on both sides of the organic polymer film pattern 17A.
Further, at FIG. 4G of the process, a Ta film 33a, an Au film 33b, and a Ta film 33c are deposited one by one by sputtering on the structure of FIG. 4F, using a structure 20 including the polymer film organic pattern 17A and the resist pattern R2A as the mask. On the hard bias patterns 16A and 16B, the electrode patterns 33A and 33B, respectively, are formed, extending on the upper surface of the magnetoresistance effect element 15 toward the root of the organic polymer film pattern 17A.
Further, by removing the organic polymer film pattern 17A at FIG. 4H of the process, an electrode layer 33 deposited on the resist pattern R2A is removed.
Conventionally, miniaturization of a magnetoresistance effect element has been achieved by shortening exposure wavelength, using an exposure optical system that has a high aperture rate (NA), and improving resist materials used in resist processes. However, the conventional miniaturization technique is coming to a turning point in view of difficulty of developing a resist material suitable for use with short wavelength, particularly in the case of miniaturization exposure technology after a 0.1 μm generation that uses an ArF excimer laser, etc.
Under the situation such as above, in the conventional manufacturing process described with reference to FIGS. 4A through 4H, the organic polymer film pattern 17A, such as PMGI, is used, and a miniaturization process that exceeds the exposure limit is performed using the etching selectivity between the resist pattern R2A and the organic polymer film pattern 17A at FIGS. 4E and 4F of the process. At FIG. 4E of the process, the conventional manufacturing method uses wet etching, which does not provide sufficient controllability of etching in the lateral etching process of FIG. 4F, which can then cause the mask pattern structure 20 that is to be used as a lift-off mask at FIG. 4G of the process, including the resist pattern R2A and the organic polymer film 17A, to fall after the process of FIG. 4F is finished. The falling of the mask pattern structure 20 greatly degrades the manufacturing yield of the magnetic head. Moreover, even if the structure 20 does not fall, control of the size of the organic polymer film pattern 17A is difficult; consequently, control of the optical core width G (refer to FIG. 3) of the magnetoresistance element 15 becomes difficult.
Although it is desirable to use a dry etching process instead of a wet etching process in order to perform the lateral etching process of FIG. 4F with a high manufacturing yield, it is difficult to obtain sufficient selectivity to dry etching by the combination of the resist film R2 and the organic polymer film 17, which is conventionally used.
Moreover, although it is effective to shorten the exposure wavelength in the exposure process of the resist pattern R2A of FIG. 4D in order to form a miniaturized element, as previously mentioned, conventional organic polymer films, such as PMGI, do not function as antireflection films. For this reason, even if an exposure light source that provides short wavelength is used, it is difficult to expose the resist pattern R2A near the exposure limit. As an antireflection film, a SiN film is conventionally known. However, when the SiN film is used instead of the organic polymer film 17, the lateral etching process like FIG. 4F cannot be performed.